How to post messages to official account timeline

We want to auto post messages to our official account periodically using LINE apis. I couldn't find any documentation related to timeline posting.

I tried sending messages using Messaging API's push_message but it didn't work. Below is the code(Python) I used:

from linebot import LineBotApi
from linebot.models import TextSendMessage

channel_access_token = "token"  # available under Messaging API section as "Channel access token (long-lived)"
user_id = "userid"  # available under Basic Settings section as "Your user ID"

line_bot_api = LineBotApi(token)
line_bot_api.push_message(user_id, msg)